<html>
<head>
<style>
    #header_div {
        background: red;
    }

    #left_pane_div {
        background: green;
        float: left;
        width: 20%
    }

    #central_div {
        background: blue;
     }
</style>

<script>
    function init() {
        var html = twitter.transform(twitter.credentialsXml(), "credentials.xsl");
    }
</script>
</head>

<body onload="init()">
    <div id="header_div"> This is the header </div>

    <div>
        <div id="left_pane_div"> This is the left pane </div>

        <div id="central_div"> This is the central widget </div>
    </div>

</body>

</html>
